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Learn SAS

Rick WicklinDecember 2, 2013 0

If you write an n x p matrix from PROC IML to a SAS data set, you'll get a data set with n rows and p columns. For some applications, it is more convenient to write the matrix in a "long format" with np observations and three columns. The first

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Rick WicklinNovember 18, 2013 0

Vectorizing the construction of a structured matrix

In using a vector-matrix language such as SAS/IML, MATLAB, or R, one of the challenges for programmers is learning how to vectorize computations. Often it is not intuitive how to program a computation so that you avoid looping over the rows and columns of a matrix. However, there are a

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Rick WicklinNovember 10, 2013 0

The GCD and LCM functions in SAS

My daughter's middle school math class recently reviewed how to compute the greatest common factor (GCF) and the least common multiple (LCM) of a set of integers. (The GCF is sometimes called the greatest common divisor, or GCD.) Both algorithms require factoring integers into a product of primes. While helping

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Rick WicklinOctober 30, 2013 0

Square root transformations: How to handle negative data values?

I was looking at someone else's SAS/IML program when I saw this line of code: y = sqrt(x<>0); The statement uses the element maximum operator (<>) in the SAS/IML language to make sure that negative value are never passed to the square root function. This little trick is a real

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Rick WicklinOctober 28, 2013 0

How to order categories in a two-way table with PROC FREQ

If you've ever tried to use PROC FREQ to create a frequency table of two character variables, you know that by default the categories for each variable are displayed in alphabetical order. A different order is sometimes more useful. For example, consider the following two-way table for the smoking status

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Rick WicklinOctober 21, 2013 0

Assign the diagonal elements of a matrix

SAS/IML programmers know that the VECDIAG matrix can be used to extract the diagonal elements of a matrix. For example, the following statements extract the diagonal of a 3 x 3 matrix: proc iml; m = {1 2 3, 4 5 6, 7 8 9}; v = vecdiag(m); /* v = {1,5,9}

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Rick WicklinOctober 18, 2013 0

Rotating matrices

This article is about rotating matrices. No, I don't mean "rotation matrices," I mean rotating matrices. As in turning a matrix 90 degrees in a clockwise or counterclockwise direction. I was reading a program written in MATLAB in which the programmer used a MATLAB function called ROT90, which rotates a

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Rick WicklinOctober 7, 2013 0

How to create a library of functions in PROC IML

What is the best way to share SAS/IML functions with your colleagues? Give them the source code? Create a function library that they can use? This article describes three techniques that make your SAS/IML functions accessible to others. As background, remember that you can define new functions and subroutines in

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Advanced Analytics | Learn SAS

Rick WicklinSeptember 30, 2013 0

Generate combinations in SAS

Last week I described how to generate permutations in SAS. A related concept is the "combination." In probability and statistics, a combination is a subset of k items chosen from a set that contains N items. Order does not matter, so although the ordered triplets (B, A, C) and (C,

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Advanced Analytics | Learn SAS

Rick WicklinSeptember 23, 2013 0

Generate permutations in SAS

I've written several articles that show how to generate permutations in SAS. In the SAS DATA step, you can use the ALLPEM subroutine to generate all permutations of a DATA step array that contain a small number (18 or fewer) elements. In addition, the PLAN procedure enables you to generate

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Learn SAS

Jim SimonSeptember 18, 2013 0

Importing CSV files into SAS datasets

Sometimes, your first impulse may not be correct, like trading in your practical sedan for a hot 2-seater. Other times, your first impulse is perfect, as in the examples below. Suppose the automobile data you wish to analyze resides in a CSV file. Naturally, your first impulse is to import

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Rick WicklinSeptember 13, 2013 0

The difference between frequencies and weights in regression analysis

This week I read an interesting blog post that led to a discussion about specifying the frequencies of observations in a regression model. In SAS software, many of the analysis procedures contain a FREQ statement for specifying frequencies and a WEIGHT statement for specifying weights in a weighted regression. Theis

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Jeff ThompsonSeptember 3, 2013 0

My transition from academia to SAS

I am passionate about teaching. My colleagues would probably say this is the understatement of the year. And it likely has something to do with the fact that both of my parents were teachers. I started my teaching career at the university level and after many years an unexpected opportunity

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Rick WicklinSeptember 3, 2013 0

Convert a string into a vector of characters

Sometimes it is useful in the SAS/IML language to convert a character string into a vector of one-character values. For example, you might want to count the frequency distribution of characters, which is easy when each character is an element of a vector. The question of how to convert a

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Shelly GoodinAugust 30, 2013 0

SAS author's tip: Using pre-defined styles

This week's SAS tip is from Kevin D. Smith and his new book PROC TEMPLATE Made Easy: A Guide for SAS Users. Kevin is a software developer at SAS with extensive experience supporting PROC TEMPLATE and underlying ODS technologies. We're excited that Kevin decided to write his book and hope

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Rick WicklinAugust 26, 2013 0

Determine the version of SAS software at run time

Recently I wrote about how to determine the age of your SAS release. Experienced SAS programmers know that you can programatically determine information about your SAS release by using certain automatic macro variables that SAS provides: SYSVER: contains the major and minor version of the SAS release SYSVLONG: contains the

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Rick WicklinAugust 19, 2013 0

Errors that cause SAS to "freeze"... and what to do about them

Even the best programmers make mistakes. For most errors, SAS software displays the nature and location of the error, returns control to the programmer, and awaits further instructions. However, there are a handful of insidious errors that cause SAS to think that a statement or program is not finished. For

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Michelle HomesAugust 6, 2013 0

Read what you need

With the pervasiveness of mobile devices, being able to read while “on the go” has been easier than ever. How many times have you found yourself in a situation where you pass the time waiting by reading something on your phone/iPad/tablet etc? With eBooks on my iPad, I find that

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Rick WicklinAugust 2, 2013 0

How old is your version of SAS? Release dates for SAS software

How old is your version of SAS software? The graph on the left shows the release dates for various releases of SAS software, beginning with SAS 8.0. The graph is based on a graph on Jiangtang Hu's blog that shows the major SAS releases. As this graph demonstrates, SAS software

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Rick WicklinJuly 29, 2013 0

Read data sets that are specified by an array of names

One of my favorite features of SAS/IML 12.1 (released with 9.3m2) is that the USE and CLOSE statements support reading data set names that are specified in a SAS/IML matrix. The IMLPlus language in SAS/IML Studio has supported this syntax since the early 2000s, so I am pleased that this

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Rick WicklinJuly 22, 2013 0

The inverse CDF method for simulating from a distribution

There are many techniques for generating random variates from a specified probability distribution such as the normal, exponential, or gamma distribution. However, one technique stands out because of its generality and simplicity: the inverse CDF sampling technique. If you know the cumulative distribution function (CDF) of a probability distribution, then

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Rick WicklinJuly 15, 2013 0

Bin observations by using custom cut points and unevenly spaced bins

It is often useful to partition observations for a continuous variable into a small number of intervals, called bins. This familiar process occurs every time that you create a histogram, such as the one on the left. In SAS you can create this histogram by calling the UNIVARIATE procedure. Optionally,

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Shelly GoodinJuly 12, 2013 0

SAS author's tip: Moving ODS output into your internet or intranet site

This week's SAS tip is from Lauren Haworth, Cynthia L. Zender, and Michele Burlew's book Output Delivery System: The Basics and Beyond. This example-driven book includes broad coverage of some of the best features of ODS. To learn more about the book and the authors, visit our Web catalog to read

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Learn SAS | Programming Tips

Charu ShankarJuly 8, 2013 0

Top 10 SAS coding efficiencies

Tried, tested and true -- I’m sure you already practice some, if not all, of these efficient techniques to save resources. I recently shared these 10 techniques with the Wisconsin Illinois SAS users group in Milwaukee. The conference ran smoothly under the incredibly able guidance of Dr. LeRoy Bessler. I’ll

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Rick WicklinJuly 8, 2013 0

How does the IF-THEN statement in SAS treat a missing value?

Every programming language has an IF-THEN statement that branches according to whether a Boolean expression is true or false. In SAS, the IF-THEN (or IF-THEN/ELSE) statement evaluates an expression and braches according to whether the expression is nonzero (true) or zero (false). The basic syntax is if numeric-expression then do-computation;

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Rick WicklinJuly 5, 2013 0

Obtain data sets from the book Statistical Programming with SAS/IML Software

On the Web site for the book Statistical Programming with SAS/IML Software, I provide instructions on how to download the sample data sets and install them so that they can be used from within SAS/IML Studio. When I wrote the book I did not anticipate that SAS users might want

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Carpenter's Guide to Innovative SAS Techniques

Shelly GoodinJune 14, 2013 0

SAS author's tip: Using the %DS2CSV macro

This week's SAS tip is from Art Carpenter and his latest book Carpenter's Guide to Innovative SAS Techniques. Art is a talented SAS user and prolific author--and was just recognized in the SAS Circle of Excellence for 30 years of using SAS software. After taking a look at this week's book

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Shelly GoodinJune 7, 2013 0

SAS author's tip: Understanding tokens

This week's SAS tip is from Michele Burlew and her book SAS Macro Programming Made Easy, Second Edition. Michele is the author of several extremely helpful SAS books. Visit her author page to learn more about her work and for additional free content. The following excerpt is from SAS Press

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Rick WicklinJune 3, 2013 0

Passing values from PROC IML into SAS procedures

A SAS user told me that he computed a vector of values in the SAS/IML language and wanted to use those values on a statement in a SAS procedure. The particular application involved wanting to use the values on the ESTIMATE and CONTRAST statements in a SAS regression procedure, but

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Learn SAS | Programming Tips

Chris HemedingerMay 20, 2013 0

Export and download any file from SAS Enterprise Guide

Last week I alluded to some very useful applications of the Copy Files task. This is one of them. If you have SAS Enterprise Guide 7.13 or later, the Copy Files task is in the Tasks->Data menu. In earlier versions, you'll have to download/install the task as a custom task.

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